Most children diagnosed with autism at age 2 years appear to have the condition at 9 years

Jun 9 2006

About three-fourths of children who are diagnosed with autism at age 2 years appear to have the condition at age 9 years, according to a report in the June issue of Archives of General Psychiatry.

Autism is a developmental condition characterized by difficulties with social interactions and communication and a tendency toward restricted and repetitive behaviors, according to background information in the article. Parents usually identify problems in their autistic children during the first year of life, but most diagnoses are not usually made until children are older. The concept of autism has recently expanded to include milder conditions known as autism spectrum disorders; these include Asperger's syndrome and pervasive developmental disorder not otherwise specified (PDD-NOS).

Catherine Lord, Ph.D., University of Michigan, Ann Arbor, and colleagues studied 192 children who had been referred to autism clinics or centers in North Carolina and Chicago and 22 control children who were developmentally delayed but not referred for or diagnosed with autism. The children were assessed at ages 2, 5 and 9 years and diagnosed using three measures: a parent interview; an observational scale that clinicians used to rate the children's social and communication behaviors; and the judgment of the clinicians who examined the children and made initial diagnoses. Each child received a best-estimate diagnosis, made by two additional psychologists or psychiatrists who reviewed all three of these measures and discussed the diagnosis until they reached a consensus.

Of the 172 children who were examined at age 9 years, 58 percent had a best-estimate diagnosis of autism, an increase from the 49 percent diagnosed at age 2 years. Overall, 67 percent of the best-estimate diagnoses were the same at age 2 years and age 9 years. More specifically, 76 percent of those diagnosed with autism at age 2 received the same diagnosis at age 9, and 90 percent of those diagnosed with an autism spectrum disorder at age 2 received a diagnosis of autism or an autism spectrum disorder at age 9. Parent interviews, observation scale scores and clinicians' judgment at age 2 years each independently predicted a diagnosis of autism at age 9 years, with clinical judgment most strongly linked.

For the diagnoses that did change between ages 2 and 9 years, 18 (8 percent) improved and 38 (18 percent) worsened. Only one in 84 children diagnosed with autism at age 2 was not diagnosed with autism or a spectrum disorder at age 9, while more than half of children diagnosed with PDD-NOS at age 2 received an autism diagnosis at age 9. "There are real questions about the usefulness of PDD-NOS as a categorical diagnosis," the authors write. "However, especially for very young children, having a way for experienced clinicians to acknowledge their uncertainly about some 2-year-olds was ultimately helpful as a means of flagging children who by age 9 years had a range of difficulties from autism to very mild social deficits. Because more than half of the children with PDD-NOS clinical diagnoses at age 2 years received best-estimate diagnoses of autism by age 9 years, health care professionals should be wary of telling parents that their young children do not have autism, only PDD-NOS."

"Diagnostic stability at age 9 years was very high for autism at age 2 years and less strong for pervasive developmental disorder not otherwise specified," they conclude. "Judgment of experienced clinicians, trained on standard instruments, consistently added to information available from parent interview and standardized observation."